Almost all the major classes of antibiotics have encountered resistances in clinical applications. The emergence of bacterial resistance to β-lactam antibiotics, macrolides, quinolones, and vancomycin is becoming a major worldwide health problem. The spread of antibiotic resistance among pathogenic bacteria imposes another serious problem for the clinical management of infectious diseases. Particularly, antibiotic resistance among Gram-positive bacteria (staphylococci, enterococci, and streptococci) is becoming increasingly serious. Entercococci, which are generally resistant to most antibiotics including penicillin, cephalosporin and aminoglycosides, used to be treated with either a combination of two antibiotics or vancomycin. However, with the recent increased use of vancomycin in methicillin-resistance Staphylococcus aureus (MRSA) infections and colitis due to colstridium fifficile, multiple resistant entercocccus faecium has been spreading. As such, the last resort for anti-infective diseases, the Vancomycin family of antibiotics, has now been gravely challenged in recent years due to the emergence of MRSA strains in clinical practice. There is an urgent need to discover novel antibacterial agents other than analogues of existing antibiotics.
A considerable amount of attention has focused recently on new RNA-binding molecules for drug discovery. The interactions between RNA and biological macromolecules are clearly essential fore many vital processes in molecular biology. In addition, the excitement over RNA-based viruses has fueled an interest in the development of potential RNA inhibitors. RNA offers several selective advantages over DNA as a therapeutic agent. First, chromosomal DNA is packaged extensively, significantly limiting its accessibility to small molecule regents. Second, DNA repair systems are available in the cell, whereas analogous enzymes for RNA repair are virtually unknown. Finally, RNA exhibits a high level of diversity in terms of tertiary folding, and therefore will likely have a greater potential for selective targeting based on structure rather than sequence.
Historically, however, RNA-based drug discovery has proved to be extremely difficult, and only a few classes of compounds are known to bind RNA with SAR information, for example aminoglycosides and cationic peptides. Discovery of RNA binders using traditional high throughput assays such as fluorescence, filter binding, SPA, SPR, etc. has proved to be equally unsuccessful.
Recently, a MS-based high throughput-screening assay has been developed. See, Hofstadler, S. A.; Griffey, R. H. Curr. Opin. Drug Discovery Dev. 2000, 3, 423-431; Hofstadler, S. A.; Griffey, R. H. Chem. Rev. (Washington, D.C.) 2001, 101, 377-390; Griffey, R. H.; Greig, M. J.; An, H.; Sasmor, H.; Manalili, S. J. Am. Chem. Soc. 1999, 121, 474-475; Sannes-Lowery, K. A.; Griffey, R. H.; Hofstadler, S. A. Anal. Biochem. 2000, 280, 264-271; Griffey, R. H.; Sannes-Lowery, K. A.; Drader, J. J.; Mohan, V.; Swayze, E. E.; Hofstadler, S. A. J. Am. Chem. Soc. 2000, 122, 9933-9938, and Griffey, R. H.; Hofstadler, S. A.; Sannes-Lowery, K. A.; Ecker, D. J.; Crooke, S. T. Proc. Natl. Acad. Sci. U.S.A. 1999, 96, 10129-10133, each of which is incorporated herein by reference in its entirety.
This assay is extremely sensitive and could detect RNA binders with Kd values ranging from nanomolar to minimolar. Coupled with mass assays to carry out competition experiments and determine the binding locations, such assays can be used to discover of novel compounds that bind to bacterial ribosomal RNA.
In view of the great importance of antibacterial compounds in animal, and particularly human health, it can be seen that there is a need for novel antibacterial agents. The present invention is therefore directed to, inter alia, such compounds and their uses, as well as other important ends.